We are trying to understand the chemistry and biology of double-stranded cleavage by the antitumor antibiotic bleomycin (BLM) and to determine the structures of the DNA lesions, in differew sequence contexts, generated by the interaction of BLM and other small molecules with DNA. We have developed a new method to synthesize a single strand of tethered oligomeric DNA with a 3'phosphoglycolate lesion in any sequence context. We have synthesized a lesion and acquired NMR spectra that have allowed us to assign almost all of the protons. Currently, we are in the process of performing molecular modeling using the 420 NOEs obtained thus far.